Plasma Kisspeptin: A Potential Biomarker of Tumor Metastasis in Patients with Ovarian Carcinoma

To the Editor: More than 15 000 women in the US die from ovarian carcinoma annually (1). The most important determinant of survival in ovarian carcinoma cases is tumor stage. Most patients presenting with disease confined to the ovaries (stage 1) can be cured, with a 5-year survival rate of >90% (1). Spread of the tumor outside the ovaries (stages 2 to 4) confers a much poorer prognosis, however. Cure is uncommon in patients with tumor spread into the pelvis (stage 2), the abdomen (stage 3), or the liver/extra-abdominal region (stage 4), with a 5-year survival rate as low as 22% (1). It is therefore critically important to develop novel biochemical markers of ovarian carcinoma to stratify patients according to prognosis. Serum cancer antigen 125 (CA125) is a useful marker for screening and monitoring disease response but cannot be reliably used for staging, because 20% of tumors do not secrete CA125 (2). There is currently no diagnostic marker of tumor spread in patients with diagnosed ovarian carcinoma. Kisspeptin, a peptide that activates the kisspeptin receptor, is encoded by the KISS1 (KiSS-1 metastasis-suppressor) gene. KISS1 expression negatively correlates with metastasis risk in lung, pancreatic, esophago-gastrointestinal, endometrial, renal cell, and bladder carcinomas (3). In ovarian carcinoma, low KISS1 expression is associated with aggressive disease and a poor prognosis, and KISS1 overexpression inhibits cell migration and reduces metastasis (4). Kisspeptin is therefore a putative metastasis suppressor in ovarian …